Electrical characteristics of MOSFETs (Charge Characteristic Qg/Qgs1/Qgd/QSW/QOSS)

Electrical characteristics of MOSFETs (Charge Characteristic Qg/Qgs1/Qgd/QSW/QOSS)

Gate charge

Because the Gate (G) input terminal of a MOSFET is insulated, the amounts of charge Q seen from the Gate are important characteristics. Figure 1.5 illustrates the definitions of gate charge characteristics.

Total gate charge Q g

The amount of charge to apply voltage (from zero to designated voltage) to gate

Gate-source charge 1 Q gs1

The amount of charge required for a MOSFET to begin to turn on (before dropping drain-source voltage)

Gate-drain charge Q gd

The amount of gate charge charged in the Miller plateau

Gate switch charge Q sw

The amount of charge stored in the gate capacitance from when the gate-source voltage has reached V th Until the end of the Miller plateau

Output charge Q oss

Drain-source charge

The definition of the gate charge amount is shown in the figure below.

Data sheet description

Characteristics Symbol Test Conditions Min Typ Max Unit
Total gate charge Qg VDD ≈ 20 V, VGS = 10 V, ID = 50 A 103 nC
VDD ≈ 20 V, VGS = 4.5 V, ID = 50 A 49
Gate-source charge 1 Qgs1 VDD ≈ 20 V, VGS = 5 V, ID = 50 A 25
Gate-drain charge Qgd 12.4
Gate switch charge QSW 23
Output charge QOSS VDS = 20 V, VGS = 0 V 85.4